The Cable Networks were originally built to support analog broadcast television services, in which programs are transmitted to all subscribers at the same time. These cable networks of the past were implemented in a system architecture known as “trunk and feeder”. The function of the trunk coaxial cable is to deliver broadband television signals from a central cable station to a plurality of distribution points. The distribution points are connected to feeder coaxial cables, which emanate from the trunk coaxial cable and contain subscriber tap off devices. In recent years, this primarily one-way analog broadcast cable networks have been significantly re-designed and upgraded through the use of optical fibers. Optical fibers have intrinsically more information carrying capacity than coaxial cables and less susceptible to electro magnetic interference (EMI). The newer optical cable based networks are intended to support high-speed digital two-way data services. One widely used cable data network architecture shown in FIG. 1 is known as Hybrid Fiber Coax (hereinafter referred to as HFC). The two directions of data flow consists of data traveling from the Cable Modem Termination System (hereinafter referred to as CMTS) 150 towards a cable modem 160 in a remote building, referred to as downstream and data traveling from a cable modem 160 towards the CMTS 150, referred to as upstream.
The HFC cable plant connects a plurality of personal computers and TV set-top boxes located in remote buildings (homes) to one another as well as to a variety of network devices and multimedia content providers. A personal computer 184 or the TV set-top box 185 is connected to the cable network via a cable modem 165 interface. The HFC cable plant consists of a central cable station 120, which contains a switch 128 for accessing multiple networks and a gateway router 124 for external communication links to the open Internet. The central cable station connects to a plurality of distribution hubs 140,145 via primary fiber optic cable 135. A distribution hub 140 contains one or more radio frequency (RF) modulators for transmitting information to, and one or more radio frequency (RF) demodulators for receiving information from, a plurality of cable modems 160,165,169 located in remote buildings. Connecting a distribution hub 140 with the subscribers in remote buildings is a secondary fiber optic cable 155 and coaxial cable 159 system. On larger HFC cable plants, the central cable station 120 may be further decomposed into a “main head-end” and “regional head-end”. On smaller HFC cable plants, the central cable station and distribution hub may be combined into a single location, referred to herein as “central cable station”.
The transmission spectrum in a typical HFC cable plant consists of a forward path with a RF frequency range of 54–750 megahertz (MHz) and return path with a RF frequency range of 5–42 MHz. In the cable plant, each broadcast signal is allocated to a channel in the transmission spectrum. In the United States the cable television systems use National Television Standards Committee (NTSC) standard, which allocates six (6) MHz to each channel. A typical HFC system reserves 54 MHz to 550 MHz of the transmission spectrum for broadcast analog channels. That leaves about 200 MHz (550 MHz–750 MHz) or approximately thirty three (33) 6 MHz channels for digital services, hereafter called the digital spectrum. Using quantized amplitude modulation—QAM64 technique, each 6 MHz channel can carry 27 Mbits/sec of information on the forward path. MPEG-2 is the standard for carrying digital services. MPEG-2 Transport is a standard for formatting and packetizing the compressed audio and video information and for transporting other data. The digital data stream from the cable operator is disassembled in the subscriber premises by the TV set-top box to find programs in the multiplexed signal. An MPEG-2 transport multiplex supports multiple programs in the same broadcast channel. MPEG-encoded packets can be output in a variety of data rates. For example, the MPEG-2 compression standard is able to encode a video program to a 3.85 Mbits/sec bit stream and packetize up to seven (7) 3.85 Mbits/sec bit streams into a single 27 Mbits/sec transport stream, i.e. on a single 6 MHz channel.
There are three forms of digital video services currently delivered over a typical HFC network to a subscriber television, through a TV set-top box. The digital spectrum is used for digital broadcast television programming, Near Video on Demand (NVOD) and Real Time Video on Demand (RT-VOD). In addition to carrying audio and video packets the MPEG2 transport carries data. On a HFC cable network, typically one 6 MHz channel is reserved to carry Internet Protocol (IP) data downstream. The Internet Protocol (IP) data flows from the Internet 110 though the central cable station 120, through the CMTS 150 to the cable modems 160,165,169 located in remote buildings and then onto the attached personal computer 184,187 or a television set-top box 180,185,189. The downstream available bandwidth for IP data on a 6 MHz slot is 27 Mbits/sec. This bandwidth of 27 Mbits/sec is typically shared by about 400 cable modems located in remote buildings (homes). The available upstream bandwidth for the same 400 homes is in the range of 3 Mbits/sec to 9 Mbites/sec. Therefore, typical available upstream bandwidth is 3 to 10 times smaller than the typical available downstream bandwidth. Thus the HFC network is an asymmetrical network with more limited upstream bandwidth that needs to be carefully managed in comparison to the downstream bandwidth.
Standardization efforts on the HFC network, its components, and the services that run on the network, are underway. CableLabs®, is a research and development consortium of cable television system operators representing North and South America. CableLabs is leading several initiatives aimed at developing interoperable interface specifications for delivering advanced multimedia services over two-way cable plant. The Data Over Cable Systems Interface Specification (DOCSIS) Radio Frequency Interface Specification describes a standard for the interface between the CMTS 150 and a cable modem 160. The DOCSIS 1.1 Radio Frequency Interface Specification and the Packet Cable Dynamic Quality-of-Service Specification details Quality of Service guarantees over a HFC network. The various DOCSIS protocol mechanisms described in the said specifications can be used to support Quality of Service (hereinafter referred to as QoS) for both upstream and downstream traffic through the cable modem 160 and the CMTS 150. Quality of Service (QoS) is a measure of performance for a transmission system that reflects its transmission quality and service availability. Key parameters include Bandwidth, indicating at least a specified bit rate, Latency, indicating the delay between request and a subsequent response and Jitter, indicating the delay between packets. Other QoS parameter encodings include Traffic Priority, Maximum Sustained Traffic Rate, Minimum Reserved Traffic Rate.
Scheduling services are designed to improve the efficiency of the poll/grant process. By specifying a scheduling service and its associated QoS parameters, the CMTS 150 can anticipate the throughput and latency needs of the traffic and provide polls and/or grants at the appropriate times. Each service is tailored to a specific type of data flow. The basic services comprise: Unsolicited Grant Service (UGS), Real-Time Polling Service (rtPS), Unsolicited Grant Service with Activity Detection (UGS-AD), Non-Real-Time Polling Service (nrtpS) and Best Effort (BE) service.
Dynamic Service Flow is a key feature of DOCSIS 1.1 QoS. The dynamic creation, modification, and deletion of service flows allows for on-demand reservation of network bandwidth resources between the CMTS 150 and the TV set-top box 185 or a personal computer 184 in the home. The principal mechanism for providing enhanced QoS is to classify packets traversing the radio frequency (RF) Media Access Control interface into a Service Flow. A Service Flow is a unidirectional flow of packets that is provided a particular Quality of Service. The cable modem 165 and Cable Modem Termination System 150 provide QoS by shaping, policing, and prioritizing traffic according to the QoS Parameter Set defined for the Service Flow. Service Flows exist in both the upstream and downstream direction, and may exist without actually being activated to carry traffic. Service Flows have a 32-bit Service Flow Identifier (SFID) assigned by the CMTS 150. All Service Flows have an SFID; active and admitted upstream Service Flows also have a 14-bit Service Identifier (SID). Incoming packets are matched to a Classifier that determines to which QoS Service Flow the packet is forwarded. The Classifier can examine the IP header of the packet. If the packet matches one of the Classifiers, it is forwarded to the Service Flow indicated by the SFID attribute of the Classifier.
Service Flows are created by the Dynamic Service Addition process (DSA). The Dynamic Service Addition (DSA) may be initiated by either the cable modem (referred to as CM herein) 165 or the CMTS 150, and may create one upstream and/or one downstream dynamic Service Flow(s). A CM 165 wishing to create an upstream and/or a downstream Service Flow sends a request to the CMTS 150 using a dynamic service addition request message (DSA-REQ). The CMTS checks the CM's authorization for the requested service(s) and whether the QoS requirements can be supported and generates an appropriate response using a dynamic service addition response message (DSA-RSP). The CM 165 concludes the transaction with an acknowledgment message (DSA-ACK).
A CM 165 that needs to change a Service Flow definition performs the following operations. The CM 165 informs the CMTS 150 using a Dynamic Service Change Request message (DSC-REQ). The CMTS 150 will decide if the referenced Service Flow can support this modification. The CMTS 150 will respond with a Dynamic Service Change Response (DSC-RSP) indicating acceptance or rejection. The CM 165 reconfigures the Service Flow if appropriate, and then will respond with a Dynamic Service Change Acknowledge (DSC-ACK).
A CM 165 wishing to delete an upstream and/or a downstream Service Flow generates a delete request to the CMTS 150 using a Dynamic Service Deletion-Request message (DSD-REQ). The CMTS 150 removes the Service Flow(s) and generates a response using a Dynamic Service Deletion-Response message (DSD-RSP). Only one upstream and/or one downstream Service Flow can be deleted per DSD-Request.
Using the afore mentioned service flow controls, the cable operator can provide special QoS to the cable modem dynamically for the video download session, as opposed to the static provisioning and reservation of resources at the time of cable modem registration. This provides a more efficient use of the available bandwidth.
Cable operators desire to use the increased bandwidth and flexibility on the HFC networks to provide narrowcast services. Narrowcast indicates specifically tailored, custom delivery of a service to a single subscriber or to a group of similar subscribers. The system used to narrowcast a video service is called Video-On-Demand (hereinafter referred to as VOD).
Typically movies and other videos of interest are digitally encoded prior to offering on a VOD system. On cable systems the content for VOD is encoded according to the various Motion Picture Experts Group (MPEG) standards. The latest standard known as MPEG-4 refers to ISO/IEC designated standard 14496, which is incorporated herein by reference in its entirety. Previous MPEG standards popular in use today are MPEG-1, referring to ISO/IEC designated standard 11172 and MPEG-2, referring to ISO/IEC designated standard 13818, both of these standards are incorporated herein by reference in their entirety.
There are three primary flavors of VOD being deployed to digital television viewers over cable networks.
One flavor is referred to as Near Video on Demand (hereinafter referred to as NVOD), wherein a single program such as a movie is broadcast at predetermined time intervals on many channels simultaneously, but staggered by 20 minutes or so from the previous channel. This guarantees a subscriber that wishes to watch the movie over NVOD, that one is available for purchase and viewing within 20 minutes at any time. If the length of a movie is 140 minutes, to achieve the guarantee of availability of the movie within 20 minutes, the cable network operator broadcasts the same movie over seven (7) separate streams. Encoded at 3.85 Mbits/sec, this single movie will occupy a 6 MHz channel or 27 Mbits/sec. On a typical HFC cable system there are a total of only 33 channels each of six (6) MHz available to all digital services. If all of the digital spectrum were allocated to NVOD, the maximum number of unique movies that can be supported by NVOD in the above example is only 33. NVOD uses up precious bandwidth (spectrum). The cable operator expects to find groups of interested and paying subscribers to be watching each stream of the staggered movie. This may not happen. The NVOD system does not provide the user control over the movie once the show has started. The user cannot pause, fast-forward or rewind the movie. The drawbacks of NVOD are thus obvious.
The second flavor of Video-on-Demand involves automatically recording the broadcast television programming onto a storage device such as a hard disk in the TV set-top box. The subscriber is able to retrieve the recorded programming at a later time and view it with complete control over the program including pause, fast-forward or rewind functionality. A TV set-top box capable of recording and playback is called Digital Video Recorder (hereinafter referred to as DVR). However, the subscriber is limited by the size of the hard disk into how much programming is available on demand. Furthermore, the user needs to select, ahead of time, programs of interest for recording against the broadcast programming schedule. Combining NVOD with DVR gives additional flexibility and control for NVOD subscribers. Given the limited broadcast spectrum, it is highly likely that only the most popular programming will find space on the broadcast schedule. Thus it is apparent, that the limited amount of accessible content is a major drawback.
The third flavor of VOD is the Real-Time VOD (hereinafter referred to as RT-VOD) system. RT-VOD system, an embodiment of which is the Media Hawk VOD system by Concurrent corporation, consists of at least one video server including a video data storage device and a streaming unit reading the video data from the video storage device to perform a video streaming process on the video data. Through a RT-VOD service a subscriber can request and watch a desired video program. The subscriber selects the desired title from a plurality of titles provided by the RT-VOD service. At the request of the subscriber, the requested video is played immediately. The subscriber has full control over the video program, to pause, fast-forward or rewind the video while it is playing. The RT-VOD system can be thought of as a DVR located in the cable network, instead of in the subscriber premises. The said RT-VOD system is shared by a plurality of subscribers. The central RT-VOD system is typically located at the distribution hub 140 of a HFC network. However unlike NVOD, a single stream of the video is meant for a single subscriber and uses the same bandwidth (spectrum) as the single NVOD stream. In the NVOD system, the cable operator expects to find a group of paying subscribers watching the instance of a movie at the same time. In the RT-VOD system, only a single subscriber pays for the same bandwidth. Therefore RT-VOD is very expensive as measured against the limited bandwidth between the cable operator and the subscriber television. RT-VOD requires a fixed amount of locked down guaranteed bandwidth (spectrum) for each instance of each stream of video delivered to the plurality of subscribers. As a very large number of titles are stored on the RT-VOD system, along with a large number of subscribers added to the network, the RT-VOD system will become unwieldy and expensive. The RT-VOD system cannot scale easily to large concurrent subscriber usage. Typical size of RT-VOD storage is in the range of a three (3) to five (5) Terra bytes. Typical RT-VOD system is provisioned to support concurrent usage by ten (10) percent of the subscriber base. If popular new movie releases were to be made available on the RT-VOD system, it is likely that concurrent usage demand from subscribers could not be met by the RT-VOD system architecture. It is also likely that storage demands of all of the non-popular, very occasionally requested videos could not be met cost effectively by the streaming RT-VOD system.
Content providers such as the Hollywood movie studios have been unwilling to release newer and more popular movies into the VOD system. The content providers would like to have a direct interactive relationship with the content consuming subscribers. The content providers would like to directly interact with the subscribers, so they can build an ongoing dynamic personalized relationship with each subscriber, without being intermediated by content aggregators and cable operators. For example, the content providers would like to understand the subscriber preferences and be able to recommend movies of interest, sell associated merchandise, etc. Towards this goal, the major movie studios are attempting direct distribution by downloading of movies from their websites hosted on the Internet to the subscribers connected to the broadband Internet through their personal computers. There are several major drawbacks in this strategy as listed below. (i) The movies reach only personal computers and do not reach televisions. Subscribers would prefer to receive movies on their televisions. (ii) The time to download a typical movie over the Internet at typical current broadband data rate, of say 1 Mbits/sec, is in the range five (5) to eight (8) hours. (iii) The cost of hosting and distributing broadband content on the Internet is prohibitively expensive.
Increasingly digital cable TV set-top boxes 180,185,189, one embodiment of which is the Scientific Atlanta Explorer 8000, are being designed and manufactured with a hard disk on board. The TV set-top box is connected to the Cable network through a DOCSIS cable modem. The TV set-top boxes have the same two-way connectivity to the network as a personal computer connected to a broadband network. The typical size of a hard disk in the TV set-top boxes is 40 Giga Bytes (GB). A typical central cable station 120 services 200,000 homes with 200,000 TV set-top boxes. Thus, aggregate hard disk storage of 8000 Terra-Bytes (8,000,000 Giga Bytes) may be available, distributed in the remote buildings (homes) connected to a typical central cable station.
A heretofore un-addressed need exists in the industry for providing a system and method for making almost unlimited amount of multimedia available on the network for on-demand consumption by paying subscribers in the homes. There is a need to support large concurrent audiences consuming varying multimedia. It is a further object of the present invention to provide a system architecture that allows the content providers to interact directly and personally with the said subscribers. All of the advantages accrued to the distribution of video by the use of the present invention, also applies equally to other type of broadband multimedia such as digital pictures, games, audio etc., video being one of the multimedia.